Process for the refining of petroleum fractions



July 17, 192s n 1,677,425

v F. C. AXTELL PRocEss Fou THE REFINING' oF rETRoLEUM FRAcTIoNs.

Filed Sept. 24, 1925 A PHMWM- l L JEP/W89 T10/v I rnANx c. AXTELL, or' SOUTH rAsAnENA, enamonnra'AssreNon To Ax'raLL :en-

snAnon LABORATORIES, INC., or Los Antennas; CALIFORNIA, A conronn'rron OF CALIFORNIA.

PROCESS FOR THE BEFINING OF PETROLEUM FRACTIONS.

Application led September 24, 1925. Serial No. 58,327.

4 As is well known to those skilled in the art, dehydrated crude petroleum is subjected to distillation in order to separate it into constituent commercial products, such as gasoline, engine distillate, kerosene, fuel oil, lubricating stock, etc. Some of these distillates, such as gasoline, kerosene, ete., are then subjected to a refining process by means of which certain impurities which they contain, such as sulphur compounds, nitrogenous bases, acids, etc., are removed, some of the refined products being subjected t'o a nal' distillation.

ln refiningl such distillates, it is usually the custom to subject the same to the action of an oxidizing agent, the object being the oxidation of the sulphur compounds and other impurities contained therein, rendering the same soluble in more or less highly concentrated sulphurie acid when the distillates are treated therewith subsequent to such oxidizing treatment. With the oxidizing agents usually employed, great diiiiculty is experienced in controlling the action thereof, as not only the impurities are oxidized, but valuable hydrocarbon constituents of such distillates,` are also attacked. This results not only in a direct loss thereof, but in an instability such that the petroleum products thus made are characterized b the fact that they become yellow upon stan ing or when subjected to the action of air and light, and possess other objectionable properties.

The above observations. are particulariy true as regards the distillates made from asphaltic base petroleums or from petroleums of mixed asphaltic and paraihn base. As islwell known to those skilled in the art, distillates from these crude petroleums are characterized by a high degree of instability, and it is almost impossible to refine these distillates in such `way as to insure colorless, stable products.

With these facts in view, it is evident that, in order to successfully oxidize the impurities contained in such distillates, an oxidizing agent which will not attack the valued hydrocarbons themselves should be employed; vand I find that persulphuric and C'aros acid, when properly used, possess this propertg. v- The gure may be regarded as a diagram or flow-sheet illustrating one series of steps 1n which my process is employed, the most essential novel steps being indicated by doubleline rectangles, and steps which may be omitted when gasoline is treated'being enclosed in dotted lines. In carrying out this invention I prefer to proceed as follows: For instance, for the production of a fine illuminating oil from California distillate, I pre-fer t'o take a cut having an initial boiling point of about 300 F., and a dry (end) point of about 510 F., with a gravity of about 40 to 41 at 60 F. by the American Petroleum Institute hy' drometer. The first preliminar-.y treatment in my process may consist in subjecting such a distillate to treatment with dilute sul huric acid containing about 5 per cent ILS 4, using about twenty pounds of this dilute acid for each barrel of the distillate treated. The oil and acid are to be very-thoroughly agitated, so that the acid assumes a, very finely divided state, and the agitation is prefer-A ably continued for from about thirty minl utes to one hour, at the end of which time the acid is allowed to settle under the action o f gravity and is separated from the distillate. The object of this treatment is the removal of certain basic compounds which are present in the distillate and which combine with the sulphurie acid and are soluble therein.

After this treatment, the distillate may then advantageously be washed with, say, one charge of water amounting to about one-- fourth the amount of the distillate, being thoroughly agitated therewith and permitted to settle and then separated therefrom.

The distillate is next treated with a solution consisting of about one pound of a caustic alkali, preferably sodium hydroxide, dissolved in about threepounds of water, for each barrel of distillate treated. This solution is to be very thorou hly agitated with the distillate, preferably At the end of this time, about one gallon of water may advantageousl be added for each barrel of distillate treate the mixture being then again agitated for about live minutes,

.after which the aqueous solution is permitted to settle and is separated from the distillate. The latter may then be washed with two or three successive lcharges of water,

or about an hour.

nary and as in part optional, the oil 1s now ready for my special oxidizing treatment, which is carried out, as follows:

My preferred oxidizing agent may be prepared by dissolving a persulphate, such. as' persulphate of sodium or of potassium, in concentrated sulphuric acid,-the degree of concentration of the sulphuricacid depending upon the nature of the distillate to be treated, the amount and character of the impurities which it may have been found to contain, and the `temperature at which the dissolving and incidental reactions take place. When the persulphate is dissolved in sulphuric acid, persulphuric acid is liberated and exists as such in the sulphuric acid solution, being slowly converted to Caros acid (HZSOS) upon standing.

For the treatment of distillate `for the production of an illuminating oil, I prefer to dissolve, at ordinary room temperature, about one pound of sodium or potassium persulphate in ten pounds of sulphuric acid containing from 97.5 to 98 per cent H2SO4; and, when solution is complete and the mixture has stood for about one hour at about 20 C., I add the resultant solution, in substantiall the amount named, to each barrel of distillate treated. The mixture, containing per'sulphuric acid and Caros acid solution and distillate, is then very thoroughly agitated for about one hour in such manner that the oxidizing agent is very completely broken up and 1s kept in a state of tine subdivision and suspension in the oil during the period of treatment. In this connection, I mention that the arrangement of the treating apparatus should be such that air,- other than that normally contained in the apparatus, is not permitted access thereto, it having been found that if relatively large quantities of air are drawn into'the mixture, as through the action of the agitator, the moisture contained in such air has a strong y tendency deleteriously to affect, by dilution Y of the acid mixture the progress and result of the reaction.

The advantages of the use of this oxidizing` agent include the facts that not only are the impurities, such as sulphur and other com unds which are contained in the oil, ren e soluble in the sulphuric acid, but

they are also dissolved by the latter as rapidthe least aiected.

After the foregoing treatment is completed, the acid sludge being ermitted `to settle and separated from the istillate, the latter may be treated with a fresh charge or charges of sulphuric acid, this acid being optionally of substantially the same strength as that which was employed in'the oxidation; but, in these latterl charges, no persulphuric acid or persulphates are employed, the purpose of these inal charges being to insure that all oxidizedcompounds are removedy from the distillates Aby solution in such sulphuric acid. For the purpose indicated, this charge or these charges of acid, used vin acid-washing, are also to be very thoroughly dispersed in a vvery finely divided state and kept in suspension in the oil for about thirty minutes each, at the end of which time they are permitted to settle and are separated; and the acid-washed oil or distillate may then be very thoroughly water-washed, as with at least three charges of water, each amounting in volume-to about one-half that of the volume of the oil; or an equivalent quantity of water may be sprayed through the oil in a well-known manner. At the end of these washing operations, or their equivalents, the oil should be practically colorless, and should remain so.

`ln case traces of acid are objectionable, the next step lmay consist in treating the oil with a dilute alkaline solution for the neutralization of any traces of acid which it may contain; and for this purpose a solution of either sodium or potassium hydrate, or sodium or potassium carbonate, may be employed, the strength of such solution being preferably of from three to ve per cent of sodium or potassium hydrate or an equivalent quantity of the alkalinel carbonates, used in quantity amounting to from onefourth to one-half pound of the dry potassium or sodium hydrate, or an lequivalent quantity of the icorbonates, for each barrel' of the distillate treated. This alkaline solution is preferably to be very thoroughly agitated with the oil for about thirt minutes, at the end of which time the a kaline solution is allowed to settle and is separated -from the oil; and the latter may then be thoroughly washed with water, substantially as before, for theremoval'of the traces of alkali which it may contain.

For the finest results, oils treated as above may advantageousl which purpose a still having a large and eicient dephlegmator is desirable, the oil being preferably distilled'with steam therefrom. In the production of an illuminating be redistilled, for

lill

oil, it is found advantageous to avoid the v use of superheated steam for this purpose, using only saturated steam, which may obtain some superlieat in passing through the still. It is alsofound advantageous, in the distillation of this illuminating oil to keep the temperature of the vapors at the top of the dephlegmator below 350 F., that is, the temperature should not at any time eX- ceed 350 F. at this point; and, as a rule, the temperature of the oil in the body of the still need not exceed about 420 F.

The steam distillate may be separated, in a Well-known manner, from the Water which accompanies it and may then be'permitted to stand quietly in a proper receptacle until the emulsified Water separates therefrom,- leaving the oilin a perfectly transparent, colorless condition, ready for the market.

An illuminating oil made from California distillate by the process above described may contain from about 0.005 to 0.015 per cent of sulphur, and may have an A. P. I. gravity of about 40.5". It should be perfectly colorless, and burn indefinitely Withoutv the production of a smoky fla-me.

The method above described foil the product-ion of an illuminating oil may, with the necessary modications, be employed for the purification and stabilization of otherdistillates, such as gasoline, engine distillates, etc; but in treating light distillates, the quantity of persulphate in sulphuric acid employed, and the strength of the sulphuric acid must be adjusted to meet the conditions. For instance, for treating a gasoline distillate, it is usuallysufficient to agitate such distillate with from labout three to five pounds of 95 per cent sulphuric acid in which from onen-fourth to one-half a pound of sodium or potassium persulphate has been dissolved (with formation of a corresponding quantity of persulphuric acid and Caros acid therein) per barrel of distillate; and, vas a rule` it is not necessary to follow this treatment with further acid treatment,-

the distillate, after separation of the acid sludge and `thorough Washing-With Water, being merely neutralized With about onefourth pound of sodium hydrate dissolved in about nineteen pounds of Water, per barrel, and then being thoroughly Washed'in the Well-lnoWn manner.

lthat described above, but the strength of the sulphuric acid employed as vehicle and solvent, and the amount of persulphate dissolved .therein, must be determined by test, by reason of the fact that lubricating oils differ so greatly as regards the chemical constitution of the hydrocarbons which they contain that a formula applicable to the treatment of all lubricating oils .cannot be given.

This process, referred to as especially suitable for usein the refining of California oils, is also valuable'in its application to the refining of oils containing more parans; but the quantity of the described reagent acid mixture required may, in the latter case, be considerably. less than is necessary in the refining of distillates from asphaltic base oils.

.The novel reagent acid mixtures above mentioned are used, substantially as described, in all embodiments/of my invention, only the preliminary treatment or the Washing or neutralizing or distillingv steps being included or omitted or varied according to the hydrocarbon treated and the' product desired. No novel apparatus being required, installations suitable for the practice of my invention can be provided at very moderate cost,I and the same installation can be used in the production of a Wide Variety of superior products, substantially free from sulphur.

l claim as my invention:

In refining petroleum oils, the treatment thereof with sulphuric acid solutions of persulphuric acid and Caros acid, substantially as herein set forth and described.

In testimony whereof, have hereunto set my hand at Los Angeles, California, this 16th day of September, 1925.

FRANKC. AXTELL. 

